[#62] Standardize yaml file extensions

Currently we have mixed extensions of .yml and .yaml, this patch is
an effort to standardize all yaml documents as .yaml

Change-Id: I7eb815584de5856bbdac9a828ccad8518e8c1729

roles/libvirt-volume/tests/main.yaml

@@ -1,6 +1,6 @@
 - name: Include test variables.
   include_vars:
-    file: vars.yml
+    file: vars.yaml
 - name: install libvirt
   include_role:
     name: libvirt-install